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• Stream OpenGL framebuffer over HTTP (via FFmpeg)

  16 juin 2022, par mOfl

  I have an OpenGL application of which rendered images need to be streamed over internet to mobile clients. Previously, it sufficed to simply record the rendering into a video file, which is already working, and now this should be extended to subsequent streaming.

  



  What is working right now :

  



  

  • Render a scene to an OpenGL framebuffer object

  


  • Capture the FBO content using NvIFR

  


  • Encode it to H.264 using NvENC (no CPU round trip required)

  


  • Download the encoded frame to host memory as a byte array

  


  • Append this frame to a video file

  


  



  None of this steps involves FFmpeg or any other library so far. I now want to replace the last step with "Stream the current frame's byte array over internet" and I assume that using FFmpeg and FFserver would be a reasonable choice for this. Am I correct ? If not, what would be the proper way ?

  



  If so, how do I approach this within my C++ code ? As pointed out, the frame is already encoded. Also, there is no sound or other stuff, simply a H.264 encoded frame as byte array that is updated irregularly and should be converted into a steady video stream. I assume that this would be FFmpeg's job and that the subsequent streaming via FFserver would be simple from there. What I don't know is how to feed my data to FFmpeg in the first place, as all FFmpeg tutorials I found (in a non-exhaustive search) work on a file or webcam/capture device as data source, not volatile data in main memory.

  



  The file mentioned above that I am already able to create is a C++ file stream to which I append each single frame, meaning that different framerates of video and rendering are not treated correctly. This also needs to be taken care of at some point.

  



  Can somebody point me in the right direction ? Can I forward data from my application to FFmpeg to build a proper video feed without writing to the hard disk ? Tutorials are greatly appreciated. By the way FFmpeg/FFserver is not mandatory. If you have a better idea for streaming of OpenGL framebuffer contents, I'm eager to know.

  


• Stream OpenGL framebuffer over HTTP (via FFmpeg)

  17 juin 2016, par mOfl

  I have an OpenGL application of which rendered images need to be streamed over internet to mobile clients. Previously, it sufficed to simply record the rendering into a video file, which is already working, and now this should be extended to subsequent streaming.

  What is working right now :

  • Render a scene to an OpenGL framebuffer object
  • Capture the FBO content using NvIFR
  • Encode it to H.264 using NvENC (no CPU round trip required)
  • Download the encoded frame to host memory as a byte array
  • Append this frame to a video file

  None of this steps involves FFmpeg or any other library so far. I now want to replace the last step with "Stream the current frame’s byte array over internet" and I assume that using FFmpeg and FFserver would be a reasonable choice for this. Am I correct ? If not, what would be the proper way ?

  If so, how do I approach this within my C++ code ? As pointed out, the frame is already encoded. Also, there is no sound or other stuff, simply a H.264 encoded frame as byte array that is updated irregularly and should be converted into a steady video stream. I assume that this would be FFmpeg’s job and that the subsequent streaming via FFserver would be simple from there. What I don’t know is how to feed my data to FFmpeg in the first place, as all FFmpeg tutorials I found (in a non-exhaustive search) work on a file or webcam/capture device as data source, not volatile data in main memory.

  The file mentioned above that I am already able to create is a C++ file stream to which I append each single frame, meaning that different framerates of video and rendering are not treated correctly. This also needs to be taken care of at some point.

  Can somebody point me in the right direction ? Can I forward data from my application to FFmpeg to build a proper video feed without writing to the hard disk ? Tutorials are greatly appreciated. By the way FFmpeg/FFserver is not mandatory. If you have a better idea for streaming of OpenGL framebuffer contents, I’m eager to know.

• ffmpeg is adding an extra new line into a box

  4 août 2017, par newbie123

  I’m overlaying weather data over my webcam stream. I put a background box filter, but the padding between the text and the box is uneven. There is "a new line" of extended box bellow the text.

  

  Why is that ? There are no empty lines in a text file I’m providing to ffmpeg. Here is my code for the ffmpeg :

  ffmpeg \
  
  -f lavfi -i anullsrc \
  
  -rtsp_transport tcp \
  
  -i "$SOURCE" \
  
  -vcodec libx264 -pix_fmt yuv420p -preset ultrafast -g 20 -b:v 1000k \
  
  -vf "drawtext="fontfile=${FONT}":textfile=${textfile}:x=5:y=55:reload=1: \
  
  fontcolor=white:fontsize=${FONTSIZE}:box=1:boxborderw=5:boxcolor=black@0.5" \
  
  -threads $THREADS -bufsize 512k \
  
  -f flv "$YOUTUBE_URL/$KEY"

  EDIT :

  I found out what the problem was. I was using printf "%s\n" "$variable1" "$variable2" to create a text file. Printf %s\n automatically prints each variable into a new line. The solution was to print the last variable without the new line. Code example :

  #!/bin/sh
  
  LC_CTYPE=en_US.utf8
  
  
  
  # Get APRS weather data from aprs.fi
  
  
  
  wxstation="S55MA-10"
  
  name="Juršče, Pivka"
  
  
  
  
  
  # Basic weather data
  
  temp="$(wget -q https://aprs.fi/weather/a/${wxstation} -O - | grep Temperature | egrep '[-+]?([0-9]*\.[0-9]+|[0-9]+)' -o)"
  
  humidity="$(wget -q https://aprs.fi/weather/a/${wxstation} -O - | grep Humidity | egrep '[-+]?([0-9]*\.[0-9]+|[0-9]+)' -o)"
  
  wind="$(wget -q https://aprs.fi/weather/a/${wxstation} -O - | grep Wind | egrep '[-+]?([0-9]*\.[0-9]+|[0-9]+)' -o | sed -n -e 2p)"
  
  rain="$(wget -q https://aprs.fi/weather/a/${wxstation} -O - | grep Rain | egrep '[-+]?([0-9]*\.[0-9]+|[0-9]+)' -o | sed -n -e 1p)"
  
  
  
  # Telemetry
  
  radioactivity="$(wget -q https://aprs.fi/telemetry/a/${wxstation} -O - | grep Radioactivity | egrep '[-+]?([0-9]*\.[0-9]+|[0-9]+)' -o | sed -n -e 5p)"
  
  
  
  printf "%s\n" "$name" "Temperature: ${temp}\°C" "Humidity: ${humidity}\%" "Wind: ${wind} m/s" "Rain: ${rain} mm/h"
  
  printf "Radioactivity: ${radioactivity} uSv/h"